As pointed out in U.S. Pat. No. 3,741,915, sodium alkene sulfonates or sodium hydroxy alkane sulfonates, and particularly the mixture of sodium salts of the addition product of SO.sub.3 with alpha olefin having from 12 to 18 carbon atoms, are known to possess excellent detergency properties. A convenient form in which these detergents are used is as an aqueous solution thereof, wherein the sodium salt or mixture of sodium salts of the alpha olefin sulfonate (generally referred to in the trade as AOS) amounts to 10 to about 50 percent by weight thereof, preferably from about 20 to about 35 percent by weight thereof. Although the detergency properties of these solutions are excellent they are very fluid. Lacking "body" these solutions are unattractive to consumers because of their watery consistency.
The patent states that additives widely known to improve the viscosity of detergent solutions, such as small amounts of "alkanol amides", were found ineffective for the particular sulfonate composition described therein. In the patent the sulfonate composition is described as follows:
"The sodium sulfonates in the new composition herein can be defined as sodium alkene sulfonates, sodium hydroxy alkane sulfonates or any combination thereof, for example, wherein the weight ratio between the two can be from about 9:1 to about 3:7, preferably from about 1:1 to about 7:3, having from 12 to 18 carbon atoms in the molecule, preferably having from 14 to 16 carbon atoms in the molecule.
"The sodium sulfonates in the new composition herein can be obtained from any source, but, preferably, are obtained by reacting an alpha olefin having from 12 to 18 carbon atoms, preferably from 14 to 16 carbon atoms, with SO.sub.3, to obtain a sulfonated addition product thereof, and thereafter the sulfonation product is reacted with sodium hydroxide to obtain a product predominating in the corresponding sodium alkene sulfonates and sodium hydroxy alkane sulfonates having the same number of carbon numbers as the reactant olefin.
"The reaction of the normal alpha olefin with SO.sub.3 in the first stage and the subsequent treatment of the sulfonated addition product with sodium hydroxide in the second stage can be carried out in any conventional manner, but in a preferred embodiment are carried out as follows. In the first stage SO.sub.3 and an alpha olefin, or a mixture of olefins, for example, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1 or octadecene-1, wherein the molar ratio of SO.sub.3 to said olefin is maintained, for example, within a range of about 0.85 to about 1.15 mols of SO.sub.3 per mole of olefin, preferably within a range of about 0.98 to about 1.05 mol of SO.sub.3 per mol of olefin. In order to help moderate the temperature within the reaction zone, a temperature regulated thin-film type reactor is employed and the SO.sub.3 is introduced therein in admixture with a dry, inert gas, such as nitrogen, air, helium, SO.sub.2, CO.sub.2, etc. Volume percent of SO.sub.3 in the incoming gaseous stream can be maintained within a range of about one to about 20 percent, preferably within a range of about three to about 10 percent. The temperature in the reaction zone can be from about 0.degree. to about 100.degree.C., but preferably from about 20.degree. to about 60.degree.C. The pressure can be, for example, from about atmospheric to about 50 pounds per square inch gauge, preferably from about five to about 15 pounds per square inch gauge.
"The time required for reaction between the olefin and SO.sub.3 is difficult to define, since the reaction is exceedingly fast. In practice, the reaction zone is so designed and the flow of reactants therethrough is so adjusted that as soon as reaction between the SO.sub.3 and the olefin is effected the sulfonation product resulting from such reaction is removed from the reaction zone. In general, the residence time of the sulfonation product can be, for example, less than about 120 seconds, preferably from about 0.1 to about 60 seconds.
"The sulfonated addition product obtained above can then be cooled to a temperature of about 15.degree. to about 30.degree.C. and the pressure reduced, for example, to about one atmosphere. Inert gases and any unreacted SO.sub.3 present are removed from the reaction mixture and can be recycled, if desired, to the first stage of the process. The product is then treated in a hydrolysis step with a molar equivalent of sodium hydroxide, based on the molar amount of SO.sub.3 employed, plus from about one to about 10 mol percent excess in sufficient water to yield a final sulfonate solution of from 10 to about 50 percent, at a temperature of about 50.degree. to about 200.degree.C., preferably about 95.degree. to about 175.degree.C., and a pressure of about atmospheric to about 240 pounds per square inch gauge, for a period sufficient for the addition product to be completely neutralized.
"The composition thus obtained can contain (1) from about 20 to about 80 percent by weight, generally from about 30 to about 70 percent by weight, of double bond positional isomers of water-soluble sodium alkene-1 sulfonic acids, including the alpha-beta, beta-gamma and gamma-delta unsaturated isomers thereof; and (2) from about 10 to about 70 percent by weight, generally from about 20 to about 60 percent by weight, of a mixture of water-soluble sodium salts of aliphatic compounds containing hydroxy and sulfonate radicals, with the sulfonate radical being on the terminal carbon and the hydroxyl radical being greater than two carbons away from said terminal carbon atom. There may also be present in an amount that can be from about two to about 20 percent by weight of the composition, but generally in the range of about five to about 15 percent thereof, a mixture of water-soluble sodium salts of alkene disulfonates and water-soluble sodium salts of hydroxy alkane disulfonates. Each of these sulfonates will also carry the same number of carbon atoms as the reactant olefin. Minor amounts of other species resulting from this reaction may also be present."